The present invention relates to controllers for seating, and the like.
Articulated seating, such as tilt back chairs, swivel chairs, and other furniture articles of the type having at least two, mutually adjustable portions, are used extensively in office environments. The mutually adjustable portions of the seating are normally interconnected by a control or controller, having springs which bias the seating into a normal, fully upright position. The controller typically includes some type of adjustment device to vary the biasing forces which resist movement of the adjustable portions of the seating from their normal position.
In the specific example of tilt back chairs, the controller may have an adjustment device to regulate the "pretension" on the back, and/or the "tilt rate" of the back, as explained hereinafter. Controller "pretension" refers to the application of an initial force or torque to the back of the chair, which retains the chair back in a normally, fully upright position. The user must apply a positive force to the chair back, which force is sufficient to overcome the controller pretension, before the chair back will tilt rearwardly. Controller "tilt rate" refers to the torque which resists rearward tilting, once the chair back begins to tilt. The controller tilt rate normally varies as a function of the angle of inclination of the back, and depends upon the type of springs used, the location of the tilt axis, and other similar factors.
Because users have widely different physical characteristics, including weight, shape, and strength, the ultimate or most comfortable controller pretension and tilt rate varies from one individual to another. FIG. 14 is a graph which illustrates the torque developed by a chair controller to resist tilting of the back (which in a static state is equal to the torque applied to the back by the user), as a function of the back's tilt angle or rotational displacement from the normally upright position of the chair back. The graph line identified by the letter "L" is an empirically derived function, and represents the controller pretension and the controller tilt rate which is generally preferred by a majority of users that weigh somewhat less than the average body weight of all chair users. The graph line identified by the letter "H" is also an empirically derived function, and represents the controller pretension and the controller tilt rate which is generally preferred by a majority of users that weigh somewhat more than the average body weight of all chair users. Individuals that have a body weight which is more than that associated with graph line "L," but less than that associated with graph line "H," will normally prefer a controller pretension and a controller tilt rate that is somewhere inbetween graph lines "L" and "H," as identified by the lines Ia, Ib, Ic and Id.
A type of seating known as "task seating" is becoming increasingly popular for use at computer terminals, and other similar work stations. Such work stations typically have more than one work surface or area between which the worker traverses, and may also be shared by several workers. Hence, a task chair cannot only be used at different areas of a work station, but may also be used by several different individuals on a regular basis, and therefore must be particularly adaptable for all types of applications, work surface heights, and tasks. The ability to adjust the controller pretension and controller tilt rate in all types of articulated seating is clearly a preferred feature. However, in task seating, such adjustment capabilities are now being considered nearly essential to the marketability of the chair. It is particularly important that those adjustments for controller pretension and/or tilt rate be capable of being made quickly and easily by the workers themselves. Preferably, the adjustments can be made by the user while actually sitting on the seating, so that the back tension can be quickly tested and easily readjusted, if necessary, to attain maximum comfort. Furthermore, it is important that the tilt function be adjustable throughout a broad range, so as to be able to adapt the chair into a comfortable configuration for a wide variety of different persons and tasks.